Abstract
Piezo1 ion channels mediate the conversion of mechanical forces into electrical signals and are critical for responsiveness to touch in metazoans. The apparent mechanical sensitivity of Piezo1 varies substantially across cellular environments, stimulating methods and protocols, raising the fundamental questions of what precise physical stimulus activates the channel and how its stimulus sensitivity is regulated. Here, we measured Piezo1 currents evoked by membrane stretch in three patch configurations, while simultaneously visualizing and measuring membrane geometry. Building on this approach, we developed protocols to minimize resting membrane curvature and tension prior to probing Piezo1 activity. We find that Piezo1 responds to lateral membrane tension with exquisite sensitivity as compared to other mechanically activated channels and that resting tension can drive channel inactivation, thereby tuning overall mechanical sensitivity of Piezo1. Our results explain how Piezo1 can function efficiently and with adaptable sensitivity as a sensor of mechanical stimulation in diverse cellular contexts.
Highlights
Mechanosensation is essential for cells ranging from bacteria, which must regulate cell volume in response to harsh osmotic stress, to Merkel cells and sensory neurons in human fingertips, which are exquisitely sensitive to gentle touch (Ranade et al, 2015)
Piezo1 is activated by both convex and concave membrane curvature in multiple patch configurations
In order to assay the influence of membrane curvature and lateral membrane tension on Piezo ion channel activity, we transiently transfected HEK293t cells with mouse Piezo1-IRES-GFP and performed electrophysiological recordings during application of negative or positive pressure to the membrane patch by using a high-speed pressure clamp system, while simultaneously imaging the membrane inside the patch pipette with high resolution (400x), differential interference contrast (DIC) microscopy
Summary
Mechanosensation is essential for cells ranging from bacteria, which must regulate cell volume in response to harsh osmotic stress, to Merkel cells and sensory neurons in human fingertips, which are exquisitely sensitive to gentle touch (Ranade et al, 2015). The two mammalian isoforms, Piezo and Piezo, are widely expressed and play key roles in many physiological processes, including vascular development, red blood cell volume regulation, lineage choice in neural stem cells, and touch sensation in Merkel cells and DRG neurons (Cahalan et al, 2015; Li et al, 2014; Maksimovic et al, 2014; Pathak et al, 2014; Ranade et al, 2014a; Woo et al, 2014). Knockout of either isoform is lethal, further emphasizing the functional importance of the protein (Ranade et al, 2014a)
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